1. Field
The present disclosure relates to techniques for communicating optical signals. More specifically, the present disclosure relates to an integrated circuit that includes an optical source.
2. Related Art
Silicon photonics is a promising technology that can provide large communication bandwidth, low latency and low power consumption for inter-chip and intra-chip connections. In the last few years, significant progress has been made in developing low-cost components for use in inter-chip and intra-chip silicon-photonic connections, including: high-bandwidth efficient silicon modulators, low-loss optical waveguides, wavelength-division-multiplexing (WDM) components, and high-speed CMOS optical-waveguide photodetectors. However, producing a suitable low-cost WDM optical source remains a challenge and poses an obstacle to implementing WDM silicon-photonic links.
The WDM optical source configuration often depends on the type of modulators used and the silicon-photonic-link architecture. For example, with electro-absorption-based broadband modulators, the WDM optical source typically needs the wavelength channels separated into different optical waveguides. Alternatively, when cascaded ring-resonator modulators are used, a WDM optical source with all the wavelength channels multiplexed in one optical waveguide is usually preferred. In both cases, the wavelength channels need to have accurate wavelength registration and channel spacing. Typically, a conventional laser source (such as a laser diode) generates a single wavelength. In order to achieve the wavelength requirements for WDM transmission, each laser source usually uses closed-loop wavelength control based on feedback from a free-space etalon filter. Moreover, the multiple laser sources, which are locked to a different wavelength grid, are then used together for a WDM link. As a consequence, laser sources for use in WDM transmission tend to be very expensive and bulky. Furthermore, it can be very difficult to integrate these discret laser sources on to silicon chips, and because future processing nodes may involve thousands (or more) optical channels, the cost of the laser sources may be prohibitive.
In an alternative approach, a single broad-spectrum light emitter may be used instead of an array of single-wavelength laser sources. For example, the broad-spectrum light emitter may include: a superluminescent diode, a broadband laser, and a mode-locked comb laser. However, because of size, cost and power-consumption limitations, none of these optical sources offers a low-cost solution for a multi-wavelength WDM laser source.
Hence, what is needed is an integrated optical source without the above-described problems.